Titanium offers an ideal advantage for biomedical and dental applications: it is nontoxic to humans. Dentistry has lagged behind medicine in practical applications of titanium. The motivation behind the previous and the proposed studies is to learn more about this metal in order to develop its full potential for dentistry. In the previous grant period (1996- 2000), we performed studies on several aspects of dental titanium casting and gained a great deal of knowledge on the casting process itself, on the experimental alloys showing promise for dentistry, and on methods of producing castings that will be acceptable for dental prostheses. The initial project period laid the groundwork for further study in all areas; this renewal proposal is a logical progression of this research program. We propose to refine what we have already learned by expanding our study to ternary and multicomponent alloys. We will study high alloy titanium (greater than 5 percent alloying elements), low alloy titanium (less than 5 percent alloying elements), and titanium intermetallic compounds. Our general hypothesis is that these refined alloy systems will produce properties equaling and possibly surpassing those of presently used dental casting alloys. Additional testing will provide more knowledge in ancillary areas, such as in reducing the reaction of the molten metal to the investment material through face-coating the mold. In addition to tensile fatigue evaluation, fracture toughness and fatigue resistance will be examined using a notchless triangular prism fracture toughness test. Mold filling will be examined by finite element modeling to predict void occurrence. Bond strength of the alloys to porcelain will be analyzed with 3-D finite element modeling. Selected alloys will be examined for cytotoxicity with typical testing methods. The specific aims to be addressed are: 1) to evaluate the proposed experimental binary, ternary, and multicomponent alloys (including intermetallics) for mechanical properties pertinent to the requirements for dental applications; 2) to examine the quality of the cast experimental alloys based on the requirements for acceptable dental prostheses in the areas of mold filling, casting accuracy, and subsurface structures; 3) to evaluate the corrosion behavior and biocompatibility of the experimental alloys; 4) to examine the characteristics of cast experimental alloys necessary for dental applications, including bond strength to porcelain, machinability, and wear behavior; and 5) to evaluate the fatigue resistance and fracture toughness of the experimental cast alloys.